Peter M. Groen / cxxopts

* Add cxxopts.hpp as a source file to executable
* Add msvc options for compiling
* Add CXXOPTS_BUILD_EXAMPLES option to CMake build
  * This is helpful when using CMake's ExternalProject_add()
  * It is ON by default, but configurable from the command-line.

Looked like it was left over from something? Saw it when testing "--some-int-val string"

This fixes support for options such as --file="folder with spaces/file".

 * Get list of groups
 * Get help details for groups

Conflicts:
	src/cxxopts.hpp

Conflicts:
	src/cxxopts.hpp
	src/example.cpp

Conflicts:
	src/cxxopts.hpp

Add an eol between each option groups